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Off circuit tap switch is not handle during the transformer is energies.
true
False
true
An Off-Circuit Tap Changer (OCTC) is a manual mechanical device used to adjust the transformer turns ratio by changing taps when the transformer is completely de-energized. Attempting to operate it while the transformer is energized would result in an open circuit or short circuit across tap contacts, leading to massive arcing and catastrophic failure of the transformer windings.
An Off-Circuit Tap Changer (OCTC) is a manual mechanical device used to adjust the transformer turns ratio by changing taps when the transformer is completely de-energized. Attempting to operate it while the transformer is energized would result in an open circuit or short circuit across tap contacts, leading to massive arcing and catastrophic failure of the transformer windings.
VsтАЛ=VpтАЛ├ЧNpтАЛNsтАЛтАЛ тАФ The turns ratio relationship defining the effect of tapping
The OCTC physically disconnects the primary or secondary winding segments from the supply and reconnects them to a different physical tap position. Because it lacks a vacuum bottle or oil-quench mechanism to handle load current, the arc produced by breaking the circuit under load would not be extinguished, causing sustained arcing that destroys the contact assembly.
OCTC requires the transformer to be isolated from all power sources.
Operation under load leads to severe arcing and internal short-circuits.
Mechanical interlocks are typically provided to prevent operation while the circuit breaker is closed.
OLTC (On-Load Tap Changer) is the alternative device designed to adjust voltage while energized.
Simple and rugged mechanical design
Lower maintenance and lower cost compared to OLTC
Requires supply interruption for voltage regulation
Not suitable for systems requiring frequent voltage adjustments
Distribution transformers
Transmission transformers where grid voltage is relatively stable
| Feature | OCTC | OLTC |
|---|---|---|
Operation Mode | De-energized | Energized/Under-load |
Always verify zero voltage via a multimeter or discharge rod before initiating tap changes.
Option B is false because operating an OCTC under load violates safety and design standards for transformer protection.
A is correct тАФ Off-circuit tap changers are strictly designed for operation only when the transformer is de-energized to prevent arcing and damage.
Always distinguish between OCTC and OLTC; if a question mentions 'on-load', it implies the use of diverter switches and transition resistors, which are absent in standard OCTC.